The hybridization of the ipso carbon in chlorobenzene is sp2.

Explanation:
Hybridization:
Hybridization is a concept in chemistry that describes the mixing of atomic orbitals to form new hybrid orbitals. These hybrid orbitals help in explaining the molecular geometry and bonding properties of molecules.

Chlorobenzene:
Chlorobenzene is an organic compound with the formula C6H5Cl. It consists of a benzene ring (C6H6) with one hydrogen atom replaced by a chlorine atom (Cl). The carbon atoms in the benzene ring are sp2 hybridized.

Hybridization of the ipso carbon:
In chlorobenzene, the ipso carbon refers to the carbon atom directly bonded to the chlorine atom. This carbon atom is also part of the benzene ring.

The benzene ring in chlorobenzene is planar, and each carbon atom in the ring is sp2 hybridized. This means that each carbon atom in the benzene ring forms three sigma bonds with other atoms or groups. Two sigma bonds are formed with neighboring carbon atoms, and one sigma bond is formed with a hydrogen atom in benzene or a chlorine atom in chlorobenzene.

Explanation of sp2 hybridization:
In sp2 hybridization, the carbon atom forms three sp2 hybrid orbitals by mixing one 2s orbital and two 2p orbitals. These three orbitals are located in a plane around the carbon atom, forming a trigonal planar geometry.

One of the sp2 hybrid orbitals overlaps with an sp2 hybrid orbital from another carbon atom to form a sigma bond, creating the carbon-carbon single bond in the benzene ring. The other two sp2 hybrid orbitals form sigma bonds with neighboring carbon atoms, completing the delocalized pi system of the benzene ring.

The remaining sp2 hybrid orbital on the ipso carbon atom forms a sigma bond with the chlorine atom, replacing one of the hydrogen atoms in benzene. This sigma bond is formed by overlap of the sp2 hybrid orbital on the carbon with a p orbital on the chlorine atom.

Summary:
The ipso carbon in chlorobenzene is sp2 hybridized. This means that it forms three sigma bonds in a trigonal planar geometry, with two sigma bonds to neighboring carbon atoms and one sigma bond to the chlorine atom. The sp2 hybridization allows for the formation of the planar benzene ring and the delocalized pi system, which contributes to the stability and unique properties of chlorobenzene.